1. Field of the Invention
The present invention relates to a structure of touch display panel and, more particularly, to an OLED touch display panel structure.
2. Description of Related Art
In recent year, the flat panel display industry has been rapidly developed, and many products have also been made in pursuit of light weight, thinness, small volume and fine image quality for developing several types of flat-panel displays to replace traditional cathode ray tube display (CRT). FIG. 1 schematically illustrates the types of known display panels. As shown in FIG. 1, the flat panel display includes liquid crystal display (LCD), plasma display panel (PDP), organic light emitting diode (OLED) display, field emission display (FED), and vacuum fluorescence display (VFD).
Among these types of flat panel displays, the organic light emitting diode display (OLED) technology is the one with great potential. OLED was first published by Eastman Kodak Co. in 1987. It has the features of thinness, light weight, self-illumination, low driving voltage, high efficiency, high contrast, high color saturation, fast response, flexibility, etc., and is therefore deemed as positively evaluated display technology following the TFT-LCD. In recent years, due to the development of mobile communications, digital products and digital televisions, the demand for high-quality full-color flat-panel displays is rapidly increased. The OLED display is provided with not only the advantages of LCD display including thinness, power-saving, and full-color display, but also the features of wide viewing angle, self-illumination, and fast response that are better than LCD.
FIG. 2 schematically illustrates the basic structure of conventional OLED display. The OLED display 200 includes a cathode layer 210, an OLED layer 220, an anode layer 230, a thin film transistor layer 240, a lower substrate 250, and an upper substrate 260, wherein the OLED layer 220 further includes a hole transporting layer (HTL) 221, an emitting layer 223, and an electron transporting layer (ETL) 225.
The light-emitting principle of OLED is such that the electrons and electric holes are injected from the cathode layer 210 and the anode layer 230 respectively by applying electric field and, after the electric holes pass through the electric hole transport sub-layer 221 and electrons pass through the electron transport sub-layer 225, the electrons and electric holes enter the light-emitting layer 223 with fluorescent characteristics and then are combined to produce excited photons, which immediately release energy and return to the ground state. The released energy will generate different colors of light based on different luminescent materials, so as to cause OLED to emit light.
The conventional OLED display 200 has a cathode layer 260 disposed below the upper substrate 260. The cathode layer 210 can be used to isolate the noise from the top of the upper substrate 260 and receive current of the pixel electrodes of the anode layer 230, so as to control the illumination of light emitting layer 223.
The conventional touch display panel includes a touch panel and a display unit overlapped with the touch panel. The touch panel is configured as an operation interface. The touch panel is transparent so that an image generated by the display unit can be viewed directly by a user without being sheltered by the touch panel. Such well known skill of the touch panel may increase additional weight and thickness of the touch display panel, and may further reduce the light penetration rate, and increase reflectance and haze of the touch display panel.
On-cell and in-cell touch technology are invented to overcome the drawbacks of traditional touch technology described above. The on-cell technology is to dispose a touch sensor on a thin film and then bond the thin film onto the upper one of the upper glass substrate layer. The in-cell touch technology is provided to integrate the touch sensor within the display unit so that the display unit is provided with the ability of the touch panel. Therefore, the touch display panel does not need to be bonded with an additional touch panel so as to simplify the assembly procedure. Such skill is generally developed by display panel manufactures.
For the on-cell touch technology, it needs a sensing layer to be configured on an upper glass substrate or needs to use an upper substrate to increase touch sensing electrode, which not only increases the manufacturing cost but also complicates the manufacturing process, and which may also lower the aperture ratio and thus higher the manufacturing cost. Therefore, it desired for the aforementioned OLED touch display panel structure to be improved.